[cordova][xwalk-2461] Remove 2 deprecated DOMLauncher checkpoints

- XWALK-2461: The DOMLauncher testing was originally requested from community, now the getSettings() method is deprecated, remove test cases of sample app DOMLauncher.
Merge pull request #1142 from haoxli/cordova/xwalk-2461

[cordova][xwalk-2461] Remove 2 deprecated DOMLauncher checkpoints